SAN DIEGO, July 23, 2013 /PRNewswire/ -- Mast Therapeutics, Inc. (NYSE MKT: MSTX) today announced results of its thorough QT/QTc study of MST-188, an investigational agent being developed to treat serious or life-threatening diseases with significant unmet needs, such as sickle cell disease and acute limb ischemia. The study met its primary endpoint and demonstrated that, based on analysis of electrocardiograms, MST-188 did not have an adverse effect on cardiac repolarization, as measured by prolongation of the QT interval. MST-188 was generally well-tolerated at both therapeutic and supratherapeutic doses.

Brian M. Culley, Chief Executive Officer, said: "I congratulate our clinical operations team for successfully executing the first clinical study of MST-188 since we acquired the program. The results from this trial augment the safety data supporting MST-188 and our belief that MST-188 will demonstrate a favorable risk/benefit profile in our on-going Phase 3 study in sickle cell disease, as well as our planned Phase 2 study in acute limb ischemia."

Details of the Thorough QT/QTc Study

The study was a single center, four-period, four-way cross-over, placebo- and positive-controlled, double-blind, randomized clinical trial in healthy volunteers that compared the effects of MST-188 at therapeutic and supratherapeutic doses to placebo and moxifloxacin (an antibiotic known to prolong the QT interval) on cardiac ventricular repolarization, specifically, Fridericia's corrected QT-Interval (QTcF) from the surface electrocardiogram. The primary endpoint was to confirm a lack of effect of MST188 on QTcF.

The QT interval represents the time required for the heart to repolarize after each beat. As prolongation of the QT interval may increase the risk for cardiac arrhythmias, the FDA requires a QT study for most new drugs. A QT study is a specialized clinical trial designed to assess whether an investigational medication has the potential to prolong the QT interval.

About Mast Therapeutics

Mast Therapeutics, Inc. is a publicly traded biopharmaceutical company headquartered in San Diego, California. The Company is leveraging the MAST (Molecular Adhesion and Sealant Technology) platform, derived from over two decades of clinical, nonclinical and manufacturing experience with purified and non-purified poloxamers, to develop MST-188, its lead product candidate, for serious or life-threatening diseases with significant unmet needs. MST-188 is a cytoprotective, hemorheologic, anti-inflammatory and anti-thrombotic agent that has potential utility in diseases or conditions characterized by microcirculatory insufficiency (endothelial dysfunction and/or impaired blood flow).

The Company is enrolling subjects in EPIC, a pivotal Phase 3 study of MST-188 in sickle cell disease. The Company plans to initiate a Phase 2 clinical study of MST-188 in acute limb ischemia, a complication of peripheral arterial disease, in late 2013 or early 2014. More information can be found on the Company's web site at www.masttherapeutics.com.

Mast Therapeutics and the corporate logo are trademarks of Mast Therapeutics, Inc.

Forward Looking StatementsMast Therapeutics cautions you that statements included in this press release that are not a description of historical facts are forward-looking statements that are based on the Company's current expectations and assumptions. Such forward-looking statements include, but are not limited to, statements regarding the Company's development plans for MST-188 in acute limb ischemia, including the timing of initiation of the planned Phase 2 study, and the Company's belief that EPIC and the planned Phase 2 clinical study in acute limb ischemia will demonstrate a favorable risk/benefit profile for MST188 in those indications. Among the factors that could cause or contribute to material differences between the Company's actual results and the expectations indicated by the forward-looking statements are risks and uncertainties that include, but are not limited to: the uncertainty of outcomes in ongoing and future nonclinical and clinical studies of MST-188 and the risk that MST-188 may not demonstrate adequate safety, efficacy or tolerability in one or more such studies; delays in the commencement of clinical studies, including as a result of difficulties in obtaining regulatory agency agreement on clinical development plans or clinical study design, opening trial sites, enrolling study subjects and manufacturing sufficient quantities of clinical trial material; the potential for institutional review boards or the FDA or other regulatory agencies to require additional nonclinical or clinical studies prior to initiation of the planned Phase 2 clinical study of MST-188 in acute limb ischemia; the risk that, even if clinical studies are successful, the FDA or other regulatory agencies may determine they are not sufficient to support a new drug application; the Company's reliance on contract research organizations (CROs), contract manufacturing organizations (CMOs), and other third parties to assist in the conduct of important aspects of development of MST-188, including clinical studies, and regulatory activities for MST-188 and that such third parties may fail to perform as expected; the Company's ability to obtain additional funding on a timely basis or on acceptable terms, or at all; the potential for the Company to delay, reduce or discontinue current and/or planned development activities, including clinical studies, partner MST-188 at inopportune times or pursue less expensive but higher-risk and/or lower return development paths if it is unable to raise sufficient additional capital as needed; and other risks and uncertainties more fully described in the Company's press releases and periodic filings with the Securities and Exchange Commission. The Company's public filings with the Securities and Exchange Commission are available at www.sec.gov.

You are cautioned not to place undue reliance on forward-looking statements, which speak only as of the date when made. Mast Therapeutics does not intend to revise or update any forward-looking statement set forth in this press release to reflect events or circumstances arising after the date hereof, except as may be required by law.